1. Concept Explanation (Exam-Focused)
Quality Control of Water deals with testing,
maintaining, and ensuring that water is safe for drinking and domestic use
as per prescribed standards.
In SSC JE / RRB JE, questions are:
- Direct
factual (limits & standards)
- Conceptual
MCQs
- Statement-based
traps (desirable vs permissible)
📌 Key Exam Point:
Water must be safe, palatable, and free from pathogens.
Objectives of Water Quality Control
✔ Protect public health
✔ Prevent water-borne diseases
✔ Ensure acceptability (taste, color, odor)
2. Important Parameters & Standards (MOST ASKED)
Physical Parameters
|
Parameter |
Acceptable Limit |
|
Turbidity |
1 NTU (max 5 NTU) |
|
Colour |
5 Hazen |
|
Taste & Odour |
Agreeable |
Chemical Parameters
|
Parameter |
Acceptable Limit |
|
pH |
6.5 – 8.5 |
|
Total Hardness |
200 mg/L (max 600) |
|
Chlorides |
250 mg/L |
|
Fluoride |
1.0 mg/L (VERY IMPORTANT) |
|
Nitrates |
45 mg/L |
Biological Parameter
✔ E. coli / Coliform = 0 per
100 mL
⚠ Exam Trap: Even 1
coliform = unsafe water
3. Important Formulas (Repeated in Exams)
1️⃣ Total Hardness
2️⃣ Temporary Hardness
3️⃣ Chlorine Demand
4️⃣ Standalone Centered Equation
(Residual Chlorine)
🧠 Mnemonic Trick:
“pH – 6.5 to 8.5 | Fluoride = ONE | Coliform = NONE”
4. Short Notes / One-Liners (Last-Day Revision)
✔ Turbidity affects disinfection
efficiency
✔ Excess fluoride causes fluorosis
✔ Hardness is not a health hazard
✔ Nitrates cause blue baby syndrome
✔ Residual chlorine ensures continued disinfection
5. PYQ Patterns (SSC JE / RRB JE)
🔹 Direct questions on pH
& fluoride limits
🔹
MCQs on coliform presence
🔹
Chlorine demand numericals
🔹
Confusion between temporary & permanent hardness
⚠ Typical Trap:
Permissible limit marked as acceptable (❌)
6. Solved Examples
Example 1 (Numerical – Chlorine Demand)
Chlorine dose = 1.0 mg/L
Residual chlorine = 0.3 mg/L
✅ Answer: 0.7 mg/L
Example 2 (Conceptual)
If coliform bacteria are present in drinking water →
❌
Water is unsafe, even if all other parameters are within limits.
7. MCQs (Exam Level – 30 Questions)
1. Acceptable pH range for drinking water is:
A) 5–6
B) 6.5–8.5
C) 7–9
D) 8–10
✅
Ans: B
2. Presence of coliform bacteria indicates:
A) Hard water
B) Turbid water
C) Fecal contamination
D) Salinity
✅
Ans: C
3. Acceptable fluoride concentration in drinking water
is:
A) 0.5 mg/L
B) 1.0 mg/L
C) 1.5 mg/L
D) 2.0 mg/L
✅
Ans: B
4. Residual chlorine should be checked after:
A) 5 min
B) 10 min
C) 30 min
D) 1 hour
✅
Ans: C
5. Temporary hardness is mainly due to:
A) Sulphates
B) Chlorides
C) Bicarbonates
D) Nitrates
✅
Ans: C
6. Turbidity in drinking water is measured in:
A) ppm
B) mg/L
C) NTU
D) Hazen
✅
Answer: C
📝
Explanation: Turbidity unit = NTU
7. Maximum permissible turbidity for drinking water is:
A) 1 NTU
B) 2 NTU
C) 5 NTU
D) 10 NTU
✅
Answer: C
8. Excess fluoride in drinking water causes:
A) Goitre
B) Fluorosis
C) Cholera
D) Typhoid
✅
Answer: B
9. Blue baby syndrome is caused by excess:
A) Chloride
B) Fluoride
C) Nitrate
D) Iron
✅
Answer: C
10. Hardness of water is mainly due to presence of:
A) Sodium salts
B) Potassium salts
C) Calcium & magnesium salts
D) Iron salts
✅
Answer: C
11. Temporary hardness is caused by:
A) Chlorides
B) Sulphates
C) Bicarbonates
D) Nitrates
✅
Answer: C
12. Permanent hardness is caused by:
A) Bicarbonates
B) Carbonates
C) Sulphates & chlorides
D) Hydroxides
✅
Answer: C
13. Acceptable limit of total hardness as per IS
standards is:
A) 100 mg/L
B) 150 mg/L
C) 200 mg/L
D) 600 mg/L
✅
Answer: C
14. Which parameter affects the efficiency of
chlorination the most?
A) Colour
B) Odour
C) Turbidity
D) Taste
✅
Answer: C
15. Residual chlorine in drinking water should be
maintained at:
A) 0.05 mg/L
B) 0.1 mg/L
C) 0.2–0.5 mg/L
D) 1.0 mg/L
✅
Answer: C
16. Chlorine demand is defined as:
A) Chlorine added
B) Chlorine remaining
C) Chlorine consumed
D) Chlorine removed
✅
Answer: C
📝
Explanation: Demand = Dose − Residual
17. If chlorine dose is 1.2 mg/L and residual chlorine is
0.4 mg/L, chlorine demand is:
A) 0.4 mg/L
B) 0.6 mg/L
C) 0.8 mg/L
D) 1.6 mg/L
✅
Answer: C
18. Presence of even one coliform per 100 mL indicates:
A) Acceptable water
B) Slight contamination
C) Unsafe water
D) Hard water
✅
Answer: C
19. Which test indicates fecal contamination of water?
A) pH test
B) Hardness test
C) Coliform test
D) Turbidity test
✅
Answer: C
20. Acceptable chloride concentration in drinking water
is:
A) 100 mg/L
B) 150 mg/L
C) 250 mg/L
D) 500 mg/L
✅
Answer: C
21. pH value less than 6.5 indicates water is:
A) Alkaline
B) Neutral
C) Acidic
D) Saline
✅
Answer: C
22. Which parameter mainly affects taste of water?
A) Turbidity
B) Chlorides
C) pH
D) Coliform
✅
Answer: B
23. Hardness of water is usually expressed as:
A) CaCO₃ equivalent
B) NaCl equivalent
C) MgSO₄ equivalent
D) CaCl₂ equivalent
✅
Answer: A
24. Which statement is TRUE?
A) Hardness causes health problems
B) Coliforms are acceptable in small quantity
C) Residual chlorine ensures continued disinfection
D) High turbidity improves chlorination
✅
Answer: C
25. Permissible limit of nitrate in drinking water is:
A) 20 mg/L
B) 30 mg/L
C) 45 mg/L
D) 100 mg/L
✅
Answer: C
26. Which of the following is NOT a physical parameter of
water?
A) Colour
B) Turbidity
C) Taste
D) pH
✅
Answer: D
27. Which metal causes reddish-brown staining of clothes
and fixtures?
A) Calcium
B) Magnesium
C) Iron
D) Sodium
✅
Answer: C
28. Water with pH = 8.0 is:
A) Acidic
B) Neutral
C) Slightly alkaline
D) Highly alkaline
✅
Answer: C
29. Which parameter has no direct health effect but
causes inconvenience?
A) Hardness
B) Nitrate
C) Fluoride
D) Coliform
✅
Answer: A
30. Which statement is INCORRECT?
A) Residual chlorine is measured after 30 minutes
B) Hardness is expressed as CaCO₃
C) Fluoride desirable limit is 1.0 mg/L
D) Presence of coliform is acceptable
✅
Answer: D
Last-Minute JE Memory Trick 🧠
“pH 6.5–8.5 | Fluoride = 1 | Nitrate = 45 | Coliform =
ZERO | Chlorine = 0.2–0.5”